The committee announced on Friday it had received a referral from the Office of Congressional Ethics, an independent investigative body, and said in a brief statement that it would formally investigate the one-time Republican presidential candidate.
A lawyer for Bachmann had previously acknowledged the investigation by the OCE and said that Bachmann was cooperating. That probe is focused in part on her short-lived presidential bid.
Bachmann, a leader in the tea party movement, announced earlier this year she would not seek re-election.
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